WO1997043218A1

WO1997043218A1 - Immobilized cell bioreactor and method of biodegrading pollutants in a fluid

Info

Publication number: WO1997043218A1
Application number: PCT/US1997/008096
Authority: WO
Inventors: Albert Daniel Powers
Original assignee: Alliedsignal Inc.
Priority date: 1996-05-14
Filing date: 1997-05-13
Publication date: 1997-11-20
Also published as: JP2000510044A; EP0902760A1; CA2255031A1; AU3124597A

Abstract

An immobilized cell bioreactor is provided, which bioreactor includes a tank (10) providing a compact and highly efficient system for biodegrading organic pollutants in a fluid. The tank (10) is generally cylindrical and includes a plurality of chambers (12, 14, 16, 18, 20), the fluid flowing sequentially through the chambers to an end chamber (20) from which the fluid is discharged. The chambers support a volume of mixed biomass media. The tank can be operated either aerobically or anaerobically in a multi-phase treatment process.

Description

IMMOBILIZED CELL BIOREACTOR AND METHOD OF BIODEGRADING POLLUTANTS IN A FLUID

Field of the Invention

The present invention is directed to a tank for treating a fluid containing impurities. More particularly, the invention provides an immobilized cell bioreactor for biodegradation of organic pollutants in an aqueous media.

Background of the Invention

As increasingly strict wastewater discharge rules are being enforced, industrial processing plants are finding that their wastewater treatment facilities are no longer adequate to meet the stricter requirements. Accordingly, there is a great need for improved treatment methods and equipment to meet these stricter requirements.

Among the methods currently employed to reduce or remove pollutants from wastewater, bioremediation is an effective and highly desirable approach. In bioremediation, pollutants serve as a food source, generally carbon and nitrogen, for microorganisms. As the microorganisms consume the pollutants, the pollutants are converted to metabolites, generally carbon dioxide and water in an aerobic process or to methane in an anaerobic process. The resulting metabolites usually have no adverse environmental effects. Bioremediation is typically accomplished as a fixed-film process, in which the microorganisms or biological media, are fixed to a support. One type of fixed-film process utilizes activated sludge containing large amounts of biomass media, commonly coupled with storage retention ponds. Phenol and phenolic compounds are commonly employed industrial chemicals used by many industries. Bioremediation has been successfully used to reduce phenol levels, most commonly by inducing phenol biodegradation using activated sludge and storage retention ponds. However, phenols at high concentrations are toxic to microorganisms, and the addition of adsorbents such as Fuller's earth and activated carbon to retention ponds appears to prevent phenols at toxic concentrations from interfering with bacterial activities, or at least to reduce such interference.

One disadvantage to the degradation of phenolics is that the process occurs slowly; a holding time of 10-20 days is not unusual . This necessitates very large storage basins requiring large tracts of land. Another disadvantage is that phenol degradation by activated sludge requires disposal of the sludge itself, which can contribute significantly to the cost of removing phenolics from waste waters. Furthermore, the activated carbon must be periodically replaced or regenerated, adding to the overall process cost both by the replacement as well as the disposal of spent carbon.

Commonly assigned U.S. Patent No. 4,983,299 to Lupton et al. (the "'299 patent"), the contents of which are incorporated in their entirety by reference herein, discloses an improved porous biomass support system used in a fixed bed reactor configuration. The system provides an aerobic oxidation achieving effluent phenol levels less than 0.1 parts per million ("ppm") at hydraulic retention times ("HRT") under 24 hours, requiring no activated carbon regeneration or replacement, and with substantially less sludge formation than obtained from currently available technology. The system utilizes a fixed mass of particulate open-celled polyurethane foam having both powdered activated carbon and aerobic phenolic degrading microorganisms entrapped within its pores.

This material is used to treat process waters generated in the making of coal tar. Such process waters include pollutants, such as ammonia, phenol, anthracene, methylene chloride, benzene, and toluene. Other chemicals found in the plant waters yield products such as naphthalene, creosote, roofing pitch and electrode binder pitch.

Using the material disclosed in the '299 patent in an aerobic fixed-film bioreactor system, that is, with the biomass media fixed to the polyurethane foam, resulted in superior performance compared to typical activated sludge systems. The bioreactor harbors microorganisms, trapped in the highly porous polyurethane foam, which consume the pollutants.

The bioreactor system incorporates a rectangular modular tank design with a 40,000 gallon capacity in a unit of approximately 11.5 feet wide, 10 feet high, and 47.5 feet long, divided into four chambers. The tank can accommodate feed rates in the range of 38 gallons per minute ("gpm") to 100 gpm, depending on the hydraulic retention time required by the particular application.

The modular design accommodates increasing capacities by employing additional units, increasing the capacity by an additional 40,000 gallons per unit. However, the capacity of each modular unit is limited due to the size that can be fabricated and shipped over the road in one vehicle. In applications where land use is limited, the modular unit cannot be implemented. Brief Description of the Drawings

Figure l is a top plan view of the immobilized cell bioreactor tank of the present invention;

Figure 2 is a partial front view of the immobilized cell bioreactor tank of Figure l;

Figure 3 is a sectional view of the immobilized cell bioreactor tank of Figures 1 and 2, taken along line 3-3 of Figure 1;

Figure 4 is a sectional view depicting the upcomer/ downcomer assembly for the immobilized cell bioreactor tank of Figures 1-3, taken along line 4-4 of Figure 1;

Figure 5 is a top plan view of the immobilized cell bioreactor tank of Figure 1, configured with a fluid inlet disposed at the lower portion of the tank;

Figure 6 is a view, partly schematic, of the flow of fluid through the chambers of the tank of Figure 5;

Figure 7 is a top plan view of the immobilized cell bioreactor tank of Figure 1, configured with a fluid inlet disposed at the upper portion of the tank;

Figure 8 is a view, partly schematic, of the flow of fluid through the chambers of the tank of Figure 7;

Figure 9 is a top plan view of an alternative embodiment of an immobilized cell bioreactor tank according to the present invention; and

Figure 10 is a sectional view taken along line 10-10 of Figure 9. Description of the Invention and Its Preferred Embodiments

The present invention provides an improved immobilized cell bioreactor for biodegradation of organic pollutants that includes a compact tank with a large fluid capacity. Further, the invention provides an improved immobilized cell bioreactor that accommodates either aerobic or anaerobic multi-pass treatment of fluid.

An immobilized cell bioreactor for biodegradation of organic pollutants in a fluid, according to the present invention, comprises a generally cylindrical tank including a plurality of chambers circumferentially disposed within the tank. The plurality of outer chambers includes a first chamber communicating with a fluid inlet, an end chamber in fluid communication with an outlet, and an intermediate chamber in fluid communication with the first chamber and the end chamber. A volume of mixed biomass media is disposed in at least the first and intermediate chambers. Fluid is introduced to the first chamber via the inlet, passes through the volume of mixed biomass media disposed in the first and intermediate chambers to the end chamber, and exits the bioreactor at the outlet.

Preferably, the mixed biomass media is formed of particulate open-celled polyurethane foam. The foam may have entrapped within its pores aerobic phenolic-degrading microorganisms. Alternatively, the foam may have entrapped within its pores powdered activated carbon and aerobic phenolic-degrading microorganisms.

According to one aspect of the invention, the cylindrical tank may further include an inner cylindrical chamber, with the plurality of chambers being disposed annularly about an outer surface of the inner cylindrical chamber. The inner cylindrical chamber forms the end chamber, with the outlet communicating with the inner cylindrical chamber. The inner cylindrical chamber may serve in pre- or post-treatment.

Preferably, each of the first and intermediate chambers includes a bottom grate at a lower portion thereof for supporting the volume of mixed biomass media disposed therein.

Also preferably, each of the first and intermediate chambers includes a top grate at a lower portion thereof such that the volume of mixed biomass media is contained between the bottom grate and the top grate.

According to a further aspect of the invention, the first and intermediate chambers are separated by a first partition wall, and the intermediate and end chambers are separated by a second partition wall. Preferably, each first and second partition walls includes a plurality of openings permitting the fluid to move from one of the first and intermediate chambers to one of the intermediate and end chambers.

A plurality of upcomers/downcomers are provided, each in the form of a pipe including a lower open end and a second end in communication with one of the plurality of openings in the partition walls. Fluid moves between the plurality of openings and the lower portion of the adjacent chamber via the open end and second end of the plurality of upcomers/downcomers.

Optionally, the inlet may be located at a lower portion of the tank, in which case the bioreactor further comprises a plurality of downcomers. The first and intermediate chambers are separated by a first partition wall, and the intermediate and end chambers are separated by a second partition wall. Each first and second partition walls includes a plurality of openings disposed at an upper portion thereof, with each of the plurality of downcomers being formed in the shape of a pipe including a lower open end disposed at the bottom of the next chamber and an upper end in communication with one of the plurality of openings in the partition walls. When the fluid level in one chamber reaches the plurality of openings in the partition wall, fluid enters the downcomer and is discharged at the lower open end into the next adjacent chamber.

Alternatively, the inlet may be located at an upper portion of the tank, in which case the bioreactor further comprises a plurality of upcomers. The first and intermediate chambers are separated by a first partition wall, and the intermediate and end chambers are separated by a second partition wall. Each first and second partition walls includes a plurality of openings disposed at an upper portion thereof. Each of the plurality of upcomers are formed in the shape of a pipe including a lower open end disposed at the bottom of the chamber and an upper end in communication with one of the plurality of openings in the partition walls. When the fluid in one chamber reaches the lower open end of the upcomer, fluid travels up the upcomer and is discharged at the one of the plurality of openings in the partition wall into the next adjacent chamber.

According to a preferred aspect of the invention, the height of the volume of biomass media in the first chamber is greater than the height of the volume of biomass media in the intermediate chamber to ensure hydraulic flow of fluid from the first chamber to the intermediate chamber. The height of media in the first chamber may exceed the height of media in the intermediate chamber by approximately four inches.

According to another embodiment, an immobilized cell bioreactor for biodegradation of organic pollutants in a fluid comprises a generally cylindrical tank including an inner cylindrical chamber and a plurality of outer chambers disposed annularly about the outer surface of the inner cylindrical chamber. Each of the plurality of outer chambers is in fluid communication with an adjacent outer chamber, and one of the plurality of chambers being in fluid communication with the inner cylindrical chamber. A fluid inlet is operatively disposed in another of the plurality of outer chambers, and an outlet is operatively connected to in the inner cylindrical chamber. A volume of mixed biomass media is disposed in the plurality of outer chambers. Fluid is introduced to the another of the plurality of outer chambers via the inlet, is passed through the volume of mixed biomass media disposed in the another of the plurality of outer chambers, is introduced to and passes through the volume of mixed biomass media disposed in each of the plurality of outer chambers, passes through the one of the plurality of chambers to the inner cylindrical chamber, and exits the bioreactor at the outlet.

Preferably, the mixed biomass media is formed of particulate open-celled polyurethane foam having entrapped within its pores and aerobic phenolic-degrading microorganisms or powdered activated carbon and aerobic phenolic-degrading microorganisms

Preferably, each of the plurality of outer chambers includes a bottom grate at a lower portion thereof and a top grate at a lower portion thereof such that the volume of mixed biomass media is contained between the bottom grate and the top grate.

Additionally, the plurality of outer chambers are separated by a plurality of partition walls, with each of the plurality of partition walls including a plurality of openings permitting the fluid to move between adjacent chambers. A plurality of upcomers/downcomers include a pipe having lower end and a second end in communication with one of the plurality of openings in the partition walls. Fluid moves between the plurality of openings and the lower portion of the adjacent chamber via the open end and second end of the plurality of upcomers/downcomers.

Preferably, the height of the volume of biomass media in each sequential chamber is less than the height of the volume of biomass media in the preceding chamber to ensure hydraulic flow of fluid from each of the plurality of outer chambers to the next adjacent chamber.

According to one alternative, the inlet is located at a lower portion of the tank, in which case the bioreactor further comprises a plurality of downcomers. Each of the plurality of outer chambers is separated from a next adjacent chamber by a partition wall including a plurality of openings disposed at an upper portion thereof. Each of the plurality of downcomers is formed in the shape of a pipe including a lower open end disposed at the bottom of the next adjacent chamber and an upper end in communication with one of the plurality of openings in the partition walls. When the fluid level in one chamber reaches the plurality of openings in the partition wall, fluid enters the downcomer and is discharged at the lower open end into the next adjacent chamber.

According to another alternative, the inlet is located at an upper portion of the tank, in which case the bioreactor further comprises a plurality of upcomers. Each of the plurality of outer chambers is separated from a next adjacent chamber by a partition wall including a plurality of openings disposed at an upper portion thereof, and each of the plurality of upcomers are formed in the shape of a pipe including a lower open end disposed at the bottom of the chamber and an upper end in communication with one of the plurality of openings in the partition walls. When the fluid in one chamber reaches the lower open end of the upcomer, fluid travels up the upcomer and is discharged at the one of the plurality of openings in the partition wall into the next adjacent chamber.

Preferably, the inner cylindrical chamber includes a pump communicating with the outlet for pumping the fluid out of the inner cylindrical chamber.

The invention further includes a method of biodegrading organic pollutants in a fluid. The method comprising the steps of introducing the fluid to a first chamber of a tank, with the first chamber being filled with a volume of mixed biomass media formed of particulate open- celled polyurethane foam having entrapped within its pores powdered activated carbon and aerobic phenolic-degrading microorganisms. The fluid is treated by passing the fluid through the first chamber in intimate contact with the mixed biomass media. The fluid is moved to an intermediate chamber filled with a volume of the mixed biomass media and treated by passing the fluid through the intermediate chamber in contact with the mixed biomass media. The treated fluid is moved to an end chamber and removed through an outlet communicating with the end chamber. The first, intermediate and end chambers are disposed in a generally cylindrical tank such that the at least the first and intermediate chambers form a plurality of outer chambers disposed annularly about the circumference of the generally cylindrical tank.

Preferably, the generally cylindrical tank includes an inner cylindrical chamber about which the plurality of outer chambers are annularly disposed, with the inner cylindrical chamber forming the end chamber, in which case the step of removing the treated fluid comprises pumping the treated fluid out of the inner cylindrical chamber with a pump. The method may further comprise the step of subsequently treating the fluid in the end chamber. Best Mode for Carrying out the Invention

Figures 1-4 are illustrations of a preferred embodiment of the immobilized cell bioreactor tank 10 according to the present invention. As will be described in more detail below, tank 10 advantageously is of a cylindrical shape and includes a plurality of chambers 12, 14, 16, 18, 20 circumferentially disposed therein, one or more of which contains a volume of mixed biomass media 80. Tank 10 advantageously provides a compact and highly efficient system for treating a fluid containing impurities. Further, when the volume of mixed biomass media 80 is of the type disclosed in the '299 patent, specifically, the particulate open-celled polyurethane foam having entrapped within its pores powdered activated carbon and aerobic phenolic-degrading microorganisms, tank 10 is highly effective in biodegrading phenolic materials in phenol wastewater in the unique manner described below.

Tank 10 utilizes a plug flow design to either aerobically or anaerobically treat wastewater in a multi- phase treatment process. Tank 10 may further utilize an inlet 22 disposed at the lower portion (schematically depicted in Figures 5 and 6) or the upper portion of the tank (schematically depicted in Figures 7 and 8) , as dictated by the particular design requirements of the system.

Referring in more detail to Figures 1 and 2, a first embodiment of the immobilized cell bioreactor tank 10 is divided into five preferably wedged-shaped chambers 12, 14, 16, 18 and 20. Wastewater or other fluid enters the first chamber 12 via inlet 22. The wastewater flows sequentially through first intermediate chamber 14, second intermediate chamber 16, and third intermediate chamber 18 into an end chamber 20. An outlet 24 disposed on end chamber 20 permits removal of the treated water from tank 10, to a publicly-owned water treatment facility for further treatment, or to be discharged into a river, as dictated by the particular application.

The interior of tank 10 is divided by various vertical partition walls to form the chambers. Specifically, first chamber 12 is bounded by a bottom wall 38, a portion 40a of an exterior cylindrical wall 40, roof 42, a first partition wall 28 and a second partition wall 30. Similarly, first intermediate chamber 14 is bounded by bottom wall 38, a portion 40b of exterior cylindrical wall 40, roof 42, second partition wall 30 and third partition wall 32.

Continuing, second intermediate chamber 16 is bounded by bottom wall 38, a portion 40c of exterior cylindrical wall 40, roof 42, third partition wall 32 and fourth partition wall 34. Third intermediate chamber 18 is bounded by bottom wall 38, a portion 40d of exterior cylindrical wall 40, roof 42, fourth partition wall 34, and fifth partition wall 36. Finally, end chamber 20 is bounded by bottom wall 38, a portion 40e of exterior cylindrical wall 40, roof 42, fifth partition wall 36 and first partition wall 28.

To form water-tight chambers, partition walls 28, 30, 32, 34 and 36 are welded at their edges to bottom wall 38, exterior cylindrical wall 40, and to the adjacent partition walls at the interior edges. Partition walls 28, 30, 32, 34, 36 may extend up and be welded to roof 42, or alternately, as depicted in Figure 3, may extend to the upper portion of the chamber. With the latter alternative, one or more vents 44 are provided on roof 42 is one or more vents 44 to permit air to circulate throughout tank 10 and be discharged through vent(s) 44.

As will be appreciated by one of ordinary skill in the art, either partition walls 28 and 32 or partition walls 30 and 36 may be formed by a single wall traversing the entire diameter of the tank 10. With the exception of first partition wall 28, each partition wall 30, 32, 34 and optionally 36 includes a plurality of holes 30a, 32a, 34a and 36a, respectively, disposed at an upper portion of the partition wall, which coupled with a plurality of upcomers/downcomers 26, depicted in detail in Figures 3 and 4, permit fluid to travel from one chamber to the next.

As will be described in greater detail, the structure of the upcomers/downcomers 26 is the same regardless of whether the structure functions as an upcomer or a downcomer, the only difference in function being how the fluid moves through the structure. When fluid is moved from the upper portion of one chamber (i.e., first chamber 12) to the lower portion of the adjacent chamber (i.e., first intermediate chamber 14) , the structure is labeled a downcomer since the fluid moves down the structure. Conversely, when the fluid is moved from the lower portion of one chamber (i.e., first chamber 12) to the upper portion of the adjacent chamber (i.e., first intermediate chamber 14) , the structure is labeled an upcomer since the fluid moves up the structure. As depicted in Figures l, 3 and 4, the plurality of upcomers/downcomers 26 are spaced along partition walls 28 disposed between adjacent chambers.

Referring to the detailed depiction of a typical upcomer/downcomer 26 in Figure 4, each upcomer/downcomer 26 is preferably fabricated from corrosion resistant or stainless steel pipe. Upcomer/downcomer 26 terminates in an open lower end 26a located at the lower portion of the chamber to permit fluid to enter or exit upcomer/downcomer, depending on the application. In the vicinity of holes 30a, 32a, 34a, 36a disposed in partition walls 30, 32, 34, 36 upcomer/downcomer 26 includes a 90° elbow 26b terminating in a flange 26c at hole 30a, 32a, 34a, 36a. Upcomer/downcomer 26 terminates in an upwardly extending open portion 26d, which in conjunction with a cleanout cap 56 disposed on roof 42 in vertical alignment with upcomer/downcomer 26, permits cleaning and maintenance of the upcomer/downcomer as required.

With reference to Figure 3, the internal structure of a typical chamber, in this case, second intermediate chamber 16 is depicted. Chamber 16 is bounded by bottom wall 38, portion 40c of exterior cylindrical wall 40, roof 42, third partition wall 32 (not shown) and fourth partition wall 34. Depending on the size of the tank 10, various stiffeners, depicted as angles 46, may be included, preferably on the exterior of tank 10. The tank is equipped with at least one, and preferably two, access assemblies 48 on the roof 42, including a manway 50 large enough to accommodate a typical worker. To reach the access assemblies 48, a ladder 52 and external scaffolding (not shown) may be provided.

A plurality of uniform nozzles 54 are positioned at various locations on the exterior cylindrical wall 40 of tank 10. These nozzles 54 facilitate a uniform tank design which can be used for many different applications, the nozzles being utilized for local temperature readings, pH balance, pressure in the vessel, etc. Additionally, tank 10 preferably includes a plurality of valves 58 (Figure 2) disposed at various locations on the lower portion of the circumference of tank 10, to permit flushing and draining of the tank as required for maintenance purposes.

Chambers 12, 14, 16 and 18 each include a lower support structure 60 and an upper support structure 70. As depicted in Figure 3, lower support structure 60 includes a plurality of angles 62 supporting a grating 64. More specifically, plurality of angles 62 includes an outer angle 65 including a vertical flange 65a secured to the inside surface 40c of exterior cylindrical wall 40 and a horizontal flange 65b extending from the upper surface of vertical flange 65a. A plurality of angles 66 run the length of the partition wall 28, 30, 32, 34, 36 and similarly include a vertical flange 66a secured to the respective partition wall and a horizontal flange 66b extending from the upper surface of vertical flange 66a. Several cross-wise support angles 67 traverse the chamber and are secured at each end to one of the partition walls. Grating 64 is supported by the horizontal flanges of angles 65, 66 and 67. As depicted in Figure 3, grating 64 may be comprised of several grating segments 64a for ease of manufacturing and/or assembly.

Upper support structure 70 is identical to lower support structure 60 and includes a plurality of angles 72 supporting a grating 74. More specifically, plurality of angles 72 includes an outer angle 75 secured to the inside surface 40c of exterior cylindrical wall 40, a plurality of angles 76 running the length of the partition wall 28, 30, 32, 34, and several cross-wise support angles 77 traversing the chamber and secured at each end to one of the partition walls. Grating 74 is supported by the horizontal flanges of angles 75, 76 and 77. Referring to Figures 3 and 4, both upper and lower gratings 64, 74 include a plurality of holes 64a, 74a to accommodate the upcomers/downcomers 26 therein. As depicted in Figure 3, grating 74 may be comprised of several grating segments 74a for ease of manufacturing and/or assembly.

In each chamber 12, 14, 16, 18, the volume of mixed biomass media 80 is contained between gratings 64, 74, exterior cylindrical wall 40 and the appropriate partition walls 28, 30, 32, 34, 36. Although mixed biomass media 80 can be any suitable biomass media contributing to the biodegradation or organic pollutants in an aqueous media, it is preferred that mixed biomass media 80 be the aforementioned particulate open-celled polyurethane foam disclosed in the '299 patent. As will be discussed, preferably each sequential chamber has a lesser volume of mixed biomass media 80 than the previous chamber, to facilitate hydraulic flow of the fluid from one chamber to the next.

Tank 10 may accommodate either an aerobic or anaerobic process . Referring to Figures 1 and 3 , an air inlet assembly 82 is provided at the lower portion of tank 10 beneath lower support structure 60. More specifically, air inlet assembly 82 includes an air inlet nozzle 84 disposed on the exterior cylindrical wall 40 communicating with numerous perforated pipes 86 disposed in the chamber. Optionally, to facilitate air flow out of the perforated pipes, a plurality of upwardly directed nozzles 88 (Figure 3) may be disposed on the perforated pipes 86. Air inlet assembly 82 further includes a support structure 90 including a horizontal support 91 on which the perforated pipe 86 rests and various vertical support legs 92. By utilizing the air inlet assembly 82, the system operates in an aerobic capacity. Ensuring that the air inlet assembly 82 remains closed results in an anaerobic treatment process.

The operation of the immobilized cell bioreactor tank 10 will now be described, with reference to Figures 5 and 6, schematically depicting the tank 10 with a bottom inlet and a bottom outlet. Fluid enters chamber 12 via inlet 22 disposed at the lower portion of the tank 10. As more fluid is introduced to chamber 12, the fluid level rises and the fluid traverses the chamber 12 in intimate contact with the volume of mixed biomass media 80. When fluid reaches the upper portion of the chamber in the vicinity of holes 30a in partition wall 30, the fluid enters downcomers 26 via holes 30a and is deposited at the lower portion of chamber 14. As with chamber 12, as more fluid enters chamber 14, the fluid level rises as the fluid traverses chamber 14 in intimate contact with the volume of mixed biomass media 80, until the fluid enters downcomers 26 via holes 32a in partition wall 32 and is deposited at the lower portion of chamber 16. It can be seen from Figure 6 that the holes 32a of partition wall 32 are disposed elevationally beneath holes 30a in partition wall 30, preferably by approximately four inches. Similarly, the upper support structure 70 of chamber 14 is located approximately four inches below the upper support structure 70 of chamber 12, and the height of the volume of biomass media 80 contained in chamber 14 is approximately four inches less than the height of the volume of biomass media 80 contained in chamber 12. This^' ensures that the fluid will hydraulically flow through chamber 12 to chamber 14, through chamber 14 to chamber 16, and so on.

Continuing, as fluid enters chamber 16 from downcomer 26, the fluid level rises as the fluid traverses chamber 16 in intimate contact with the volume of mixed biomass media 80, until the fluid enters downcomers 26 via holes 34a in partition wall 34 and is deposited at the lower portion of chamber 18. Holes 34a of partition wall 34 are disposed elevationally beneath holes 32a in partition wall 32, the upper support structure 70 of chamber 16 is located below the upper support structure 70 of chamber 14, and the height of biomass media 80 in chamber 16 is less than the height of biomass media 80 in chamber 14, all of which ensures hydraulic fluid flow. Once again, the fluid level in chamber 18 rises as the fluid traverses chamber 18 in intimate contact with the volume of mixed biomass media 80, until the fluid reaches the upper surface of partition wall 36, whereupon the fluid will flow over the partition wall 36 into chamber 20 to exit chamber 20 at outlet 24. It will be appreciated by one of ordinary skill in the art that partition wall 36 may optionally include a plurality of holes 36a and downcomers 26, if desired.

While it is preferred that the fluid be brought into the bottom portion of the chamber, as depicted in Figures 5 and 6, since it is believed that better results are achieved if the fluid flows upward (without the assistance of gravity) through the mixed biomass media, the tank 10 may optionally be configured with inlet 22 disposed at the upper portion of tank 10, as depicted in Figures 7 and 8. In this configuration, fluid enters chamber 12 via inlet 22 disposed at the upper portion of tank 10. Fluid travels down the chamber in intimate contact with the volume of mixed biomass media 80 to the lower portion 12a of the chamber 12. As the lower portion 12a is filled, fluid will be forced to enter upcomer 26, and a continuing flow of fluid through chamber 12 will force the liquid to flow upwardly through upcomer 26 until the liquid reaches hole 30a in partition wall 30. Upon flowing through hole 30a, the water enters chamber 14 and travels downwardly in intimate contact with the volume of mixed biomass media 80 to the lower portion 14a of chamber 14. The fluid moves up upcomer 26 to be deposited in chamber 16. The fluid traverses chambers 16 and 18 in a similar manner, and the fluid is deposited by upcomer 26 into chamber 20, whereupon it exits the tank at outlet 24. As in Figure 6, the levels of the location of the holes in the partition wall, the level of the upper support structure 70, and the height of biomass media in each chamber is approximately four inches lower than that of the preceding chamber, to ensure hydraulic flow of the fluid from one chamber to the next.

An alternate embodiment of an immobilized cell bioreactor tank is depicted in Figures 9 and 10. Tank 100 includes eight circumferentially disposed wedged-shaped outer chambers 101-108 and a central cylindrical chamber 110. The particular number of outside chambers is not critical and is dictated by design considerations such as the number of times it is desired that the fluid pass through the mixed biomass media. As in the first embodiment, fluid enters the first chamber 101 via an inlet disposed either at the upper portion or lower portion of the tank. The fluid will flow sequentially through chambers 101-108 until it enters the central chamber 110. In this configuration, the central chamber 110 may serve as a tank for further treatment, such as pH treatment or clarifier, or a sediment chamber if pellets are a problem. Central chamber 110 includes at least one, and preferably two, vertical pumps 112 to remove the fluid from central chamber 110 to the appropriate destination.

Preferably, with the exception of the mixed biomass media, all components of the system are made of carbon steel coated for corrosion resistance, corrosion resistant steel or stainless steel, welded to provide fluid-tight seams. It is also preferred that the entire vessel be cold-tar epoxy lined for further corrosion resistance. A powdered activated carbon may be used as a coating on all support surfaces of the volume of mixed biomass media as dictated by the design requirements.

In either configuration, it can be appreciated by one of ordinary skill in the art that tank 10 or 100 advantageously provides a compact design for tank capacities in the order of 80,000 gallons, 100,000 gallons, 120,000 gallons or greater. For instance, the outer diameter of the 80,000 gallon capacity tank 10 is only approximately 37 feet (38 feet for tank 100 so as to accommodate central chamber 110) ; the outer diameter of the 100,000 gallon capacity tank 10 is only approximately 41.5 feet (42.5 feet for tank 100); and the outer diameter of the 120,000 gallon capacity tank 10 is only approximately 45.5 feet (46 feet for the tank 100) . Furthermore, the tank 10, 100 of the present invention can be fabricated in the shop and erected in the field, due to the more compact design. Tank 10, 100 permits biological treatment of fluid without any reduction in feed rate over the rectangular modular design and with a surface area reduced by approximately 20% from the rectangular modular design. It will be readily seen by one of ordinary skill in the art that the present invention fulfills all of the objects set forth above. After reading the foregoing specification, one of ordinary skill will be able to effect various changes, substitutions of equivalents and various other aspects of the invention as broadly disclosed herein.

It is therefore intended that the protection granted hereon be limited only by the definition contained in the appended claims and equivalents thereof.

Claims

What is claimed is:

1. An immobilized cell bioreactor for biodegradation of organic pollutants in a fluid, comprising: a generally cylindrical tank including a plurality of chambers circumferentially disposed within the generally cylindrical tank, the plurality of chambers including a first chamber communicating with a fluid inlet, an end chamber in fluid communication with an outlet, and an intermediate chamber in fluid communication with the first chamber and the end chamber; and a volume of mixed biomass media disposed in at least the first and intermediate chambers; wherein fluid is introduced to the first chamber via the inlet, passes through the volume of mixed biomass media disposed in the first and intermediate chambers to the end chamber, and exits the bioreactor at the outlet.

2. The bioreactor of claim 1, wherein the mixed biomass media is formed of particulate open-celled polyurethane foam having entrapped within its pores powdered activated carbon and aerobic phenolic-degrading microorganisms.

3. The bioreactor of claim l, wherein the mixed biomass media is formed of particulate open-celled polyurethane foam having entrapped within its pores aerobic phenolic-degrading microorganisms.

4. The bioreactor of claim l, wherein the cylindrical tank further includes an inner cylindrical chamber, the plurality of chambers being disposed annularly about an outer surface of the inner cylindrical chamber, the inner cylindrical chamber forming the end chamber, and wherein the outlet communicates with the inner cylindrical chamber.

5. The bioreactor of claim 1, wherein each of the first and intermediate chambers includes a bottom grate at a lower portion thereof for supporting the volume of mixed biomass media disposed therein.

6. The bioreactor of claim 5, wherein each of the first and intermediate chambers includes a top grate at a lower portion thereof such that the volume of mixed biomass media is contained between the bottom grate and the top grate. 0

7. The bioreactor of claim l, wherein the first and intermediate chambers are separated by a first partition wall, and wherein the intermediate and end chambers are separated by a second partition wall.

-> 8. The bioreactor of claim 7, wherein each first and second partition walls includes a plurality of openings permitting the fluid to move from one of the first and intermediate chambers to one of the intermediate and end chambers. 0

9. The bioreactor of claim 8, further comprising a plurality of upcomers/downcomers, each in the form of a pipe including a lower open end and a second end in communication with one of the plurality of openings in the 5 partition walls, wherein fluid moves between the plurality of openings and the lower portion of the adjacent chamber via the open end and second end of the plurality of upcomers/downcomers.

10. The bioreactor of claim 1, wherein the inlet is 0 located at a lower portion of the tank, the bioreactor further comprising a plurality of downcomers, wherein the first and intermediate chambers are separated by a first partition wall, and wherein the intermediate and end chambers are separated by a second partition wall, each 5 first and second partition walls including a plurality of openings disposed at an upper portion thereof, each of the plurality of downcomers being formed in the shape of a pipe including a lower open end disposed at the bottom of the next chamber and an upper end in communication with one of the plurality of openings in the partition walls, wherein when the fluid level in one chamber reaches the plurality of openings in the partition wall, fluid enters the downcomer and is discharged at the lower open end into the next adjacent chamber.